Alex Salmond's Scottish Government has been rapped by the advertising watchdog for claiming the Edinburgh Zoo pandas as a "gift" that demonstrates the close relationship between Scotland and China.

The arrival of the bears was in fact part of a "commercial arrangement" between the zoo and the Communist authorities, according to a ruling from the Advertising Standards Authority, which banned future claims that the animals were provided without payment.

In press adverts, Mr Salmond's SNP administration boasted that China's "gifting" of Tian Tian and Yan Guang showed that Scotland had developed an especially close relationship with the world's fastest-growing country.

However after investigating the funding of the pandas, the ASA ruled that ordinary people would deem them to have been acquired as a result of a commercial agreement. In exchange for the pandas – the first to arrive in the UK for 17 years – Edinburgh Zoo's owner, the Royal Zoological Society of Scotland, is paying China £640,000 annually for 10 years to fund panda conservation.

The ASA banned Mr Salmond's government from repeating the claim.

Edinburgh Zoo, which was experiencing falling visitor numbers, is hoping the pandas will revive its financial fortunes. But they have not come cheap: their enclosures have also cost £250,000 and the animals' food, including imported bamboo, costs £70,000 a year.

In December, Mr Salmond, Scotland's First Minister, travelled to China for a trade mission timed to coincide with the pandas' arrival in Edinburgh onboard a FedEx Panda Express jet. To mark the public relations coup, the Scottish Government placed newspaper adverts featuring a picture of Tian Tian. The ad said: "Now, in a symbolic gesture of friendship between the countries, and following five years of political and diplomatic talks, the Chinese are gifting two giant pandas to live in Scotland, under the custodianship of Edinburgh Zoo."

The charities Animal Concern and Scotland for Animals claimed that was misleading because they understood the bears had been leased to the zoo by China at substantial cost.

The Scottish Government said it had not paid any money to China and quoted the Chinese ambassador, His Excellency Mr Liu Xiaoming, as saying: "This historical agreement is a gift to the people of the UK from China."

The ASA said: "We considered that consumers would interpret the terms 'gift' and 'gifting' to mean that the pandas were given without payment."